1. Field of the Invention
The present invention relates generally to the manufacture of plastic objects and more particularly fiberglass reinforced polyester articles which may be foam-filled for use as surfboards, boats and the like.
2. Prior Art
Until recently foamed-filled objects such as surfboards were fabricated from the inside out. For example, a block of rigid foam was shaped by cutting and sanding to the desired shape and the shaped block was coated with reinforced resin, sanded, smoothed and coated with a decorative coating. However, it has been recognized that such steps are time consuming and involve substantial hand labor, causing the finished parts to be expensive. Furthermore, because of the amount of hand labor required, no two objects were exactly same and the skill of the craftsman was too important an ingredient in the appearance of the final object.
Various methods have been used in an attempt to form foam-filled hollow objects from a resin shell. Such patents include Australian Pat. Nos. 211,422; 242,233 and 251,057. In addition, such method are disclosed in U.S. Pat. Nos. 2,753,642; 2,879,793; 3,487,134; 3,673,617; 3,802,010; 3,929,549; 4,065,337; 4,073,049; 4,119,583; 4,256,803; 4,268,571 and 4,383,955.
The typical method of forming a hollow object is to form two mating halves and then join them along their outer edge as typified by Australian Pat. No. 251,057. The difficulty with this method is that the joint is typically formed at an inherent point of weakness and if the object, such as a surfboard, strikes a rock or other obstruction it is very likely to split along the seam. Other edge treatments are handled by forming a flange along the outer edge which again forms a point of weakness as well as causing an unsightly rim around the edge of the product. Such method is shown in U.S. Pat. No. 4,065,337 particularly in FIG. 16 and reference character 17. Other objects are joined in a manner which does not have any particular strength and rely upon the foam for strength such as typified by U.S. Pat. No. 4,119,583 in FIG. 2. Thus there is a need for a process for forming a hollow object made from resin which has a smooth exterior surface and which does not have a point of weakness. However, perhaps just as importantly, there is a need for a process for forming a hollow object made from resin in which during the construction of the object, the interior of the surface thereof is readily accessible to permit relatively easy and therefore cost effective manufacture of such objects. Furthermore, there is a need for a process for accomplishing such fabrication in which the structure of the object is inherently strong utilizing surfaces which are resilient and durable even when such objects are subjected to substantial impact against hard objects.